Human cultured fibroblasts and Raji and peripheral blood mononuclear cells have been compared as substrates for the immunofluorescent detection of antiactin microfilament antibodies in sera from chronic liver disease. Raji and mononuclear cells, which exhibit a rich microfilament network, proved to be the most sensitive substrates for this purpose. The clinical relevance of these findings in the diagnosis of "autoimmune" chronic liver disease is discussed.